1. Field of the Invention
The present invention generally relates to leveling and polishing optical fibers, and more particularly, to an apparatus and method for leveling or balancing optical fibers relative to each other prior to conducting a polishing process to ensure polishing uniformity.
2. Description of the Related Art
Optical fibers are very light, very fragile, and have very small dimensions. During their initial manufacture, there are practical limitations on the lengths of optical fibers that can be drawn. Therefore, the connections between the fibers to create longer designated lengths of fiber are accomplished by splicing. In addition, optical fibers or optical devices must be connected to pieces of terminal equipment, such as optical transmitters and optical receivers, to create functioning optical systems.
The nature of the fibers themselves, both in the material used in their fabrication and in the minute physical dimensions involved, combined with submicron alignment requirements, make connectorization operations difficult. Problems with efficient transfer of energy, minimized optical reflections, and mechanical integrity must be addressed. The complexities of interconnecting the fibers demands careful attention to connector design and a high level of precision in polishing operations.
Optical losses caused by poor connections or poor polishing operations may take many forms. Of course, lateral or axial misalignment of the fibers will cause less than optimal light transfer. Care should also be taken to reduce Fresnel reflection losses, which may be introduced by both the glass-to-air and air-to-glass interfaces if end separation between fibers is excessive. Also, the quality of both fiber ends has an effect on the power coupling. For example, rough or unpolished fiber ends not only contribute to separation losses, they may also scratch or fracture an adjacent polished fiber end. Losses may also occur if the fiber ends lack perpendicularity when joined, which may be caused by uneven polishing. Still other losses may occur where the fiber ends are over polished, thereby producing convex shaped ends that affect the transfer of light.
Before conducting the polishing step, special holding jigs or fixtures, such as the aligning device 100 in FIG. 1, are used in an effort to align the fibers relative to each other before contact with a polishing apparatus. As shown in FIG. 1, the fibers 110 are threaded through aligning stems or receptacles 120 so as to protrude below the base 130. Note that the illustrated length of the fiber ends 110a protruding below the base 130 has been exaggerated for clarity. Also, each of the fiber ends are typically surrounded by a ceramic material, such as zirconia, to provide support and protection for the fiber ends. The details of the ceramic material have been omitted for clarity. As shown in the schematic side view in FIG. 2, if the individual fibers 110 are not evenly aligned relative to each other, the ends of the fibers 110a will experience different polishing rates, which can cause some of the alignment losses discussed above, such as lack of perpendicularity, rough edges, or excessive separation. Again, the dimensions in FIG. 2 have been exaggerated to illustrate the non-alignment problem. In practice, the alignment precision would be at a submicron level, which makes conventional direct visual inspection ineffective.
Any defects caused by misalignment during the polishing process are therefore not discovered until the subsequent testing phase. The defective optical fibers must then be reworked and retested, which results in a loss of throughput and decreased efficiency.
Accordingly, there exists a need for a leveling apparatus and method of precisely leveling or balancing the optical fibers relative to each other, prior to the polishing step, to ensure polishing uniformity and to reduce the number of defective optical fibers.